1. Field of the Invention
The present invention relates to the field of contactors and specifically to contactor actuation timing.
2. Discussion of Related Art
A “contactor” is an electrically controlled switch used for switching an electrical power circuit, similar to a relay except with higher current ratings. An electromagnetic ‘actuator’ is typically that part of the contactor mechanism which electrically controls the switching, i.e. opening and closing the electrical contacts of the switch by activation of a coil in the contactor to operate the movable contacts.
It is a known technique to time the operation of a contactor in an effort to make the closing/opening of contacts at the low power point of the AC cycle (i.e. zero crossing) in order to reduce the damaging effects of arcing on the separable contacts. Arcing at the contacts upon their separation or closure will erode the expensive, high conductivity metals used at the surfaces of the contacts and may eventually require replacement of the contacts or the entire contactor mechanism. Thus, in the known art, the efforts to reduce arcing have tended to be elaborate in terms of equipment or process, or both, and most often involve the monitoring of the current waveform(s) to achieve the maximum accuracy of timing. But, the monitoring of the current involves the provision of current transformers (CTs), which are expensive in terms of money and physical space within the equipment.
Thus in certain instances there may be a need for a more space efficient and cost efficient contactor operation system which can still prevent contact erosion and save costly conductive metal at the separable contacts.